What is the freeze method

The freeze() method is used to freeze an object. Freezing an object does not allow adding new properties to an object, prevents removing, and prevents changing the enumerability, configurability, or writability of existing properties. i.e. It returns the passed object and does not create a frozen copy.

  const obj = {
    prop: 100,
  };

  Object.freeze(obj);
  obj.prop = 200; // Throws an error in strict mode

  console.log(obj.prop); //100

Remember freezing is only applied to the top-level properties in objects but not for nested objects. For example, let's try to freeze user object which has employment details as nested object and observe that details have been changed.

  const user = {
    name: "John",
    employment: {
      department: "IT",
    },
  };

  Object.freeze(user);
  user.employment.department = "HR";

Note: It causes a TypeError if the argument passed is not an object.